Plasma processing method and apparatus

ABSTRACT

The interior of a vacuum chamber is maintained at a specified pressure by introducing a specified gas into the vacuum chamber having a plasma trap provided therein. Simultaneously, therewith, evacuation of the chamber is performed by a pump as an evacuating device, and a high-frequency power of 100 MHz is supplied to a counter electrode by counter-electrode use high-frequency power supply. Thus, uniform plasma is generated within the vacuum chamber, where plasma processing such as etching, deposition, and surface reforming can be carried out uniformly with a substrate placed on a substrate electrode.

This application is a divisional application of Ser. No. 09/511,398,filed Feb. 23, 2000 now U.S. Pat. No. 6,808,759.

BACKGROUND OF THE INVENTION

The present invention relates to plasma processing methods such as dryetching, sputtering, and plasma CVD, as well as apparatuses therefor, tobe used for manufacture of semiconductor or other electron devices andmicromachines. More particularly, the present invention relates to aplasma processing method and apparatus for the use of plasma excitedwith high-frequency power of VHF or UHF band.

The present invention further relates to a matching box for a plasmaprocessing apparatus to be used for impedance matching in supplyinghigh-frequency power of VHF band, in particular, to a counter electrodefor plasma excitation or to an antenna, and relates to a plasmaprocessing method and apparatus using plasma excited with thehigh-frequency power of VHF band.

Japanese Laid-Open Patent Publication No. 8-83696 describes that the useof high-density plasma is important in order to meet the trend towardmicrostructures of semiconductors and other electron devices.Furthermore, low electron temperature plasma has recently been receivingattention by virtue of its high electron density and low electrontemperature.

In the case where a gas having a high negativity, i.e., a gas that tendsto generate negative ions, such as Cl₂, SF₆, is formed into plasma, whenthe electron temperature becomes about 3 eV or lower, larger amounts ofnegative ions are generated than with higher electron temperatures.Taking advantage of this phenomenon makes it possible to prevent etchingconfiguration abnormalities, so-called notch, which may occur whenpositive charges are accumulated at the bottom of micro-patterns due toexcessive incidence of positive ions. This allows etching of extremelymicro patterns to be achieved with high precision.

Also, in the case where a gas containing carbon and fluorine, such asC_(X)F_(y) or C_(x)H_(y)F_(z) (where x, y, z are natural numbers), whichis generally used for etching of insulating films such as silicon oxide,is formed into plasma, when the electron temperature becomes about 3 eVor lower, gas dissociation is suppressed more than with higher electrontemperatures, where, in particular, generation of F atoms, F radicalsand the like is suppressed. Because F atoms, F radicals and the like arehigher in the rate of silicon etching, insulating film etching can becarried out at larger selection ratios than silicon etching with lowerelectron temperatures.

Also, when the electron temperature becomes 3 eV or lower, iontemperature and plasma potential also becomes lower, so that ion damageto the substrate in plasma CVD can be reduced.

As a technique capable of generating plasma having low electrontemperature, plasma sources using high-frequency power of VHF band orUHF band are now receiving attention.

FIG. 15 is a sectional view of a dual-frequency excitation parallel-flatplate type plasma processing apparatus. Referring to FIG. 15, while theinterior of a vacuum chamber 201 is maintained at a specified pressureby introducing a specified gas from a gas supply unit 202 into thevacuum chamber 201 and simultaneously performing evacuation by a pump203 as an evacuating device, a high-frequency power of 100 MHz issupplied to a counter electrode 205 by acounter-electrode-use-high-frequency power supply 204. Then, plasma isgenerated in the vacuum chamber 201, where plasma processing such asetching, deposition, and surface reforming can be carried out on asubstrate 207 placed on a substrate electrode 206. In this case, asshown in FIG. 15, by supplying high-frequency power also to thesubstrate electrode 206 by a substrate-electrode-use-high-frequencypower supply 208, ion energy that reaches the substrate 207 can becontrolled. In addition, the counter electrode 205 is insulated from thevacuum chamber 201 by an insulating ring 211.

FIG. 16 is a sectional view of a plasma processing apparatus which wehave already proposed and which has an antenna type plasma sourcemounted thereon. Referring to FIG. 16, while the interior of a vacuumchamber 301 is maintained at a specified pressure by introducing aspecified gas from a gas supply unit 302 into the vacuum chamber 301 andsimultaneously performing evacuation by a pump 303 as an evacuatingdevice, a high-frequency power of 100 MHz is supplied to a spiralantenna 313 on a dielectric window 314 by an antenna-use-high-frequencypower supply 312. Then, plasma is generated in the vacuum chamber 301 byelectromagnetic waves radiated into the vacuum chamber 301, where plasmaprocessing such as etching, deposition, and surface reforming can becarried out on a substrate 307 placed on a substrate electrode 306. Inthis case, as shown in FIG. 16, by supplying high-frequency power alsoto the substrate electrode 306 by asubstrate-electrode-use-high-frequency power supply 308, ion energy thatreaches the substrate 307 can be controlled.

However, there has been an issue that the conventional methods shown inFIGS. 15 and 16 have difficulty in obtaining uniform plasma generation.

FIG. 17 shows results of measuring ion saturation current density at aposition just 20 mm above the substrate 207 in the plasma processingapparatus of FIG. 15. Conditions for plasma generation are gas type ofCl₂ and gas flow rate of 100 sccm, a pressure of 1 Pa, and ahigh-frequency power of 2 kW. It can be understood from FIG. 17 thatplasma density is higher in peripheral regions.

FIG. 18 shows results of measuring ion saturation current density at aposition just 20 mm above the substrate 307 in the plasma processingapparatus of FIG. 16. Conditions for plasma generation are gas type ofCl₂ and gas flow rate of 100 sccm, a pressure of 1 Pa, and ahigh-frequency power of 2 kW. It can be understood from FIG. 18 thatplasma density is higher in peripheral regions.

Such nonuniformity of plasma is a phenomenon that could not be seen withthe frequency of the high-frequency power of 50 MHz or less. Whereas the50 MHz or higher high-frequency power needs to be used in order to lowerthe electron temperature of plasma, there are produced, in thisfrequency band, not only an advantage that plasma is generated by thecounter electrode or antenna being capacitively or inductively coupledto the plasma, but also an advantage that plasma is generated byelectromagnetic waves, which are radiated from the counter electrode orantenna, propagating on the surface of the plasma. In peripheral regionsof the vacuum chamber, which serve as reflecting surfaces for theelectromagnetic waves that have propagated on the surface of the plasma,stronger electric fields are developed so that thick plasma isgenerated.

Also, as described above, in the case where a gas having a highnegativity, i.e., a gas that tends to generate negative ions, such asCl₂, SF₆, is formed into plasma, when the electron temperature becomesabout 3 eV or lower, larger amounts of negative ions are generated thanwith higher electron temperatures. Taking advantage of this phenomenonmakes it possible to prevent a phenomenon that perpendicularity of theincident angle of ions onto the substrate worsens when positive chargesare accumulated at the bottom of micro-patterns due to excessiveincidence of positive ions. This allows etching of extremely micropatterns to be achieved with high precision. Besides, that is anexpectation for process improvement making use of the high reactivity ofnegative ions.

Also, in the case where a gas containing carbon and fluorine, such asC_(x)F_(y) or C_(x)H_(y)F_(z) (where x, y, z are natural numbers), whichis generally used for etching of insulating films such as silicon oxide,is formed into plasma, when the electron temperature becomes about 3 eVor lower, gas dissociation is suppressed more than with higher electrontemperatures, where, in particular, generation of F atoms, F radicalsand the like is suppressed. Because F atoms, F radicals and the like arehigher in the rate of silicon etching, insulating film etching can becarried out at larger selection ratios than silicon etching with lowerelectron temperatures.

Also, when the electron temperature becomes 3 eV or lower, iontemperature and plasma potential also become lower, so that ion damageto the substrate in plasma CVD can be reduced.

It is plasma sources using high-frequency power of VHF band that iscurrently receiving attention as a technique capable of generatingplasma low in electron temperature and capable of generating plasmasuperior in ignitability.

FIG. 24 is a sectional view of a dual-frequency excitation parallel-flatplate type plasma processing apparatus. Referring to FIG. 24, while theinterior of a vacuum chamber 401 is maintained at a specified pressureby introducing a specified gas from a gas supply unit 402 into thevacuum chamber 401 and simultaneously performing evacuation by a pump403 as an evacuating device, a high-frequency power of 100 MHz issupplied to a counter electrode 407 via a matching box 405 and ahigh-frequency coupling device (mount) 406 by acounter-electrode-use-high-frequency power supply 404. Then, plasma isgenerated in the vacuum chamber 401, where plasma processing such asetching, deposition, and surface reforming can be carried out on asubstrate 409 placed on a substrate electrode 408. In this case, asshown in FIG. 24, by also supplying high-frequency power to thesubstrate electrode 408 by a substrate-electrode-use-high-frequencypower supply 410, ion energy that reaches the substrate 409 can becontrolled. In addition, the counter electrode 407 is insulated from thevacuum chamber 401 by an insulating ring 411. The matching box 405comprises a high-frequency input terminal 412, a first variablecapacitor 413, a high-frequency output terminal 414, a second variablecapacitor 415, a first motor 416, a second motor 417, and a motorcontrol circuit 418.

However, there has been an issue that the conventional method shown inFIG. 24 has difficulty in obtaining uniform plasma generation.

FIG. 25 shows results of measuring ion saturation current density at aposition just 20 mm above the substrate 409 in the plasma processingapparatus of FIG. 24. Conditions for plasma generation are gas type ofCl₂ and gas flow rate of 100 sccm, a pressure of 2 Pa and ahigh-frequency power of 1 kW. Also, as shown in FIG. 24, the secondvariable capacitor 415 is disposed on one side of the measuring positionin FIG. 25. It can be understood from FIG. 25 that plasma density ishigher on one side of the measuring position, i.e., just below thesecond variable capacitor 415.

Such nonuniformity of plasma is a phenomenon that could not be seen withthe frequency of the high-frequency power of 50 MHz or less. Whereas the50 MHz or higher high-frequency power needs to be used in order to lowerthe electron temperature of plasma, there develops, in this frequencyband, a potential distribution in the counter electrode 407. It can bededuced that this potential distribution, affected by the placement ofthe second variable capacitor 415 within the matching box 405, acts tostrengthen the electric fields just below the second variable capacitor415, resulting in nonuniformity of plasma generation.

Such a phenomenon could be seen with such an arrangement as shown inFIG. 26 in which a spiral antenna 420 is used instead of the counterelectrode 407. In the prior art example shown in FIG. 26, a dielectricwindow 421 is used.

SUMMARY OF THE INVENTION

In view of these issues of the prior art, an object of the presentinvention is to provide a plasma processing method and apparatus, aswell as a matching box for a plasma processing apparatus, capable ofgenerating uniform plasma.

In order to achieve the above object, the present invention has thefollowing constitutions.

In accomplishing these and other aspects, according to a 1st aspect ofthe present invention, there is provided a plasma processing method forgenerating plasma within a vacuum chamber and processing a substrateplaced on a substrate electrode within the vacuum chamber. The methodcomprises generating the plasma by supplying a high-frequency powerhaving a frequency of 50 MHz to 3 GHz to a counter electrode providedopposite to the substrate while interior of the vacuum chamber iscontrolled to a specified pressure by introducing gas into the vacuumchamber and, simultaneously therewith, evacuating the interior of thevacuum chamber. The substrate is processed using the generated plasmawhile plasma distribution of the plasma on the substrate is controlledby an annular, groove-like plasma trap provided opposite to thesubstrate.

According to a 2nd aspect of the present invention, there is provided aplasma processing method for generating plasma within a vacuum chamberand processing a substrate placed on a substrate electrode within thevacuum chamber. The method comprises generating the plasma by radiatingelectromagnetic waves into the vacuum chamber via a dielectric windowprovided opposite to the substrate by supplying a high-frequency powerhaving a frequency of 50 MHz to 3 GHz to an antenna while the interiorof the vacuum chamber is controlled at a specified pressure byintroducing gas into the vacuum chamber and, simultaneously therewith,evacuating the interior of the vacuum chamber. The substrate isprocessed using the generated plasma while plasma distribution of theplasma on the substrate is controlled by an annular, groove-like plasmatrap provided opposite to the substrate.

According to a 3rd aspect of the present invention, there is provided aplasma processing method according to the 1st aspect, wherein thesubstrate is processed while a portion surrounded by the plasma trap outof a surface forming an inner wall surface of the vacuum chamber andopposing the substrate has an area 0.5 to 2.5 times that of thesubstrate.

According to a 4th aspect of the present invention, there is provided aplasma processing method according to the 1st aspect, wherein thesubstrate is processed while the plasma trap has a groove width of 3 mmto 50 mm.

According to a 5th aspect of the present invention, there is provided aplasma processing method according to the 1st aspect, wherein thesubstrate is processed while the plasma has a groove depth of not lessthan 5 mm.

According to a 6th aspect of the present invention, there is provided aplasma processing method according to the 1st aspect, wherein thesubstrate is processed while the plasma trap is provided in the counterelectrode.

According to a 7th aspect of the present invention, there is provided aplasma processing method according to the 1st aspect, wherein the plasmais generated while the plasma trap is provided outside an insulatingring for insulating the vacuum chamber and the counter electrode fromeach other.

According to an 8th aspect of the present invention, there is provided aplasma processing method according to the 1st aspect, wherein the plasmais generated while the plasma trap is provided between the counterelectrode and an insulating ring for insulating the vacuum chamber andthe counter electrode from each other.

According to a 9th aspect of the present invention, there is provided aplasma processing method according to the 1st aspect, wherein the plasmais generated while the plasma trap is provided between the vacuumchamber and an insulating ring for insulating the vacuum chamber and thecounter electrode from each other.

According to a 10th of the present invention, there is provided a plasmaprocessing method according to the 2nd aspect, wherein the plasma isgenerated while the plasma trap is provided in the dielectric window.

According to an 11th aspect of the present invention, there is provideda plasma processing method according to the 2nd aspect, wherein theplasma is generated while the plasma trap is provided outside thedielectric window.

According to a 12th aspect of the present invention, there is provided aplasma processing method according to the 2nd aspect, wherein the plasmais generated while the plasma trap is provided between the vacuumchamber and the dielectric window.

According to a 13th aspect of the present invention, there is provided aplasma processing method according to the 1st aspect, wherein the plasmais generated while DC magnetic fields are absent within the vacuumchamber.

According to a 14th aspect of the present invention, there is provided aplasma processing apparatus comprising a vacuum chamber; a gas supplyunit for supplying gas into the vacuum chamber; an evacuating device forevacuating the interior of the vacuum chamber; a substrate electrode forplacing thereon a substrate within the vacuum chamber; a counterelectrode provided opposite to the substrate electrode; high-frequencypower supply capable of supplying a high-frequency power having afrequency of 50 MHz to 3 GHz to the counter electrode; and an annular,groove-like plasma trap provided opposite to the substrate.

According to a 15th aspect of the present invention, there is provided aplasma processing apparatus comprising: a vacuum chamber; a gas supplyunit for supplying gas into the vacuum chamber; an evacuating device forevacuating the interior of the vacuum chamber; a substrate electrode forplacing thereon a substrate within the vacuum chamber; a dielectricwindow provided opposite to the substrate electrode; an antenna forradiating electromagnetic waves into the vacuum chamber via thedielectric window; a high-frequency power supply capable of supplying ahigh-frequency power having a frequency of 50 MHz to 3 GHz to theantenna; and an annular, groove-like plasma trap provided opposite tothe substrate.

According to a 16th aspect of the present invention, there is provided aplasma processing apparatus according to the 14th aspect, wherein aportion surrounded by the plasma trap out of a surface forming an innerwall surface of the vacuum chamber and opposing the substrate has anarea 0.5 to 2.5 times that of the substrate.

According to a 17th aspect of the present invention, there is provided aplasma processing apparatus according to the 14th aspect, wherein theplasma trap has a groove width of 3 mm to 50 mm.

According to a 18th aspect of the present invention, there is provided aplasma processing apparatus according to the 14th or 15th aspect,wherein the plasma trap has a groove depth of not less than 5 mm.

According to a 19th aspect of the present invention, there is provided aplasma processing apparatus according to the 14th aspect, wherein theplasma trap is provided in the counter electrode.

According to a 20th aspect of the present invention, there is provided aplasma processing apparatus according to the 14th aspect, wherein theplasma trap is provided in an insulating ring for insulating the vacuumchamber and the counter electrode from each other.

According to a 21st aspect of the present invention, there is provided aplasma processing apparatus according to the 14th aspect, wherein theplasma trap is provided outside an insulating ring for insulating thevacuum chamber and the counter electrode from each other.

According to a 22nd aspect of the present invention, there is provided aplasma processing apparatus according to the 14th aspect, wherein theplasma trap is provided between the counter electrode and an insulatingring for insulating the vacuum chamber and the counter electrode fromeach other.

According to a 23rd aspect of the present invention, there is provided aplasma processing apparatus according to the 14th aspect, wherein theplasma trap is provided between the vacuum chamber and an insulatingring for insulating the vacuum chamber and the counter electrode fromeach other.

According to a 24th aspect of the present invention, there is provided aplasma processing apparatus according to the 15th aspect, wherein theplasma trap is provided in the dielectric window.

According to a 25th aspect of the present invention, there is provided aplasma processing apparatus according to the 15th aspect, wherein theplasma trap is provided outside the dielectric window.

According to a 26th aspect of the present invention, there is provided aplasma processing apparatus according to the 15th aspect, wherein theplasma trap is provided between the vacuum chamber and the dielectricwindow.

According to a 27th aspect of the present invention, there is provided aplasma processing apparatus according to the 14th aspect, wherein nocoil or permanent magnet for applying DC magnetic fields is providedwithin the vacuum chamber.

According to a 28th aspect of the present invention, there is provided aplasma processing apparatus according to the 1st aspect, furthercomprising a matching box for use in the plasma processing apparatus andfor taking impedance matching in supplying high-frequency power to aload. The matching box comprises a high-frequency input terminal; afirst reactive element having one end connected to the high-frequencyinput terminal and the other end connected to a matching box casing; ahigh-frequency output terminal; and a second reactive element having oneend connected to the high-frequency input terminal and the other endconnected to the high-frequency output terminal. The second reactiveelement and the high-frequency output terminal are so arranged that thesecond reactive element is located on a straight line passing through acenter axis of the high-frequency output terminal.

According to a 29th aspect of the present invention, there is provided aplasma processing apparatus according to the 28th aspect, wherein thefirst reactive element and the second reactive element are capacitors,respectively.

According to a 30th aspect of the present invention, there is provided amatching box for use in a plasma processing apparatus and for takingimpedance matching in supplying high-frequency power to a load. Thematching box comprises a high-frequency input terminal; a first reactiveelement having one end connected to the high-frequency input terminaland the other end connected to a matching box casing; a high-frequencyoutput terminal; and a second reactive element having one end connectedto the high-frequency input terminal and the other end connected to thehigh-frequency output terminal. The second reactive element and thehigh-frequency output terminal are so arranged that the second reactiveelement is located on a straight line passing through a center axis ofthe high-frequency output terminal.

According to a 31st aspect of the present invention, there is provided amatching box for a plasma processing apparatus according to the 30thaspect, wherein the second reactive element and the high-frequencyoutput terminal are arranged so that a straight line passing through acenter axis of the second reactive element and a straight line passingthrough the center axis of the high-frequency output terminal aregenerally coincident with each other.

According to a 32nd aspect of the present invention, there is provided amatching box for a plasma processing apparatus according to the 30thaspect, wherein the first reactive element and the second reactiveelement are capacitors, respectively.

According to a 33rd aspect of the present invention, there is provided amatching box for a plasma processing apparatus according to the 30thaspect, wherein the first reactive element and the second reactiveelement are arranged so that a straight line passing through a centeraxis of the second reactive element and a straight line passing througha center axis of the first reactive element are generally coincidentwith each other.

According to a 34th aspect of the present invention, there is provided amatching box for a plasma processing apparatus according to the 30thaspect, wherein the high-frequency output terminal is the other enditself of the second reactive element.

According to a 35th aspect of the present invention, there is provided aplasma processing method for generating plasma within a vacuum chamberand processing a substrate placed on a substrate electrode within thevacuum chamber. The method comprises arranging a straight line passingthrough a center axis of the high-frequency coupling device, a straightline passing through a center axis of the counter electrode or antenna,and a straight line passing through a center axis of the substrate so asto be generally coincident together. The interior of the vacuum chambermaintained at a specified pressure by introducing a gas into the vacuumchamber and, simultaneously therewith, exhausting the interior of thevacuum chamber. The plasma is generated by applying a high-frequencypower having a frequency of 50 MHz to 300 MHz to a counter electrode orantenna provided opposite to the substrate via the matching box asdefined in the 30th aspect and a high-frequency coupling device providedto connect a high-frequency output terminal of the matching box and thecounter electrode or antenna to each other. The substrate is thenprocessed by using generated plasma.

According to a 36th aspect of the present invention, there is provided aplasma processing method according to the 35th aspect, in which thefollowing additional steps are accomplished before maintaining theinterior of the vacuum chamber at the specified pressure. A straightline passing through a center axis of the high-frequency output terminaland a straight line passing through the center axis of thehigh-frequency coupling device as arranged so as to be generallycoincident with each other. The plasma is generated with the straightline passing through the center axis of the high-frequency outputterminal and the straight line passing through the center axis of thehigh-frequency coupling device being generally coincident with eachother.

According to a 37th aspect of the present invention, there is provided aplasma processing method according to the 35th aspect, in which thefollowing additional steps are accomplishing before maintaining theinterior of the vacuum chamber at the specified pressure. The firstreactive element and the second reactive element are arranged so that astraight line passing through a center axis of the second reactiveelement and a straight line passing through a center axis of the firstreactive element are generally coincident with each other. The plasma isgenerated with the straight line passing through the center axis of thesecond reactive element and the straight line passing through the centeraxis of the first reactive element being generally coincident with eachother.

According to a 38th aspect of the present invention, there is provided aplasma processing method according to the 35th aspect, in which beforemaintaining the interior of the vacuum chamber at the specifiedpressure, the high-frequency output terminal is arranged so as to be theother end itself of the second reactive element, and the plasma isgenerated with the high-frequency output terminal being the other enditself of the second reactive element.

According to a 39th aspect of the present invention, there is provided aplasma processing method according to the 35th aspect, in which beforecontrolling the interior of the vacuum chamber at the specifiedpressure, a substantial distance is arranged from the other end of thesecond reactive element to the counter electrode or antenna so as not tobe more than 1/10 of the wavelength of the high-frequency power. Theplasma is generated with the substantial distance from the other end ofthe second reactive element to the counter electrode or antenna beingnot more than 1/10 of the wavelength of the high-frequency power.

According to a 40th aspect of the present invention, there is provided aplasma processing method for generating plasma within a vacuum chamberand processing a substrate placed on a substrate electrode within thevacuum chamber. The method comprises arranging a straight line passingthrough a center axis of the high-frequency coupling device, a straightline passing through a center axis of the counter electrode or antenna,and a straight line passing through a center axis of the substrate so asto be generally coincident together. The interior of the vacuum chamberis maintained at a specified pressure by introducing a gas into thevacuum chamber and, simultaneously therewith, the interior of the vacuumchamber is exhausted. The plasma is generated by applying ahigh-frequency power having a frequency of 50 MHz to 300 MHz to acounter electrode or antenna provided opposite to the substrate via thematching box as defined in the 30th aspect and a high-frequency couplingdevice provided to connect a high-frequency output terminal of thematching box and the counter electrode or antenna to each other, and thesubstrate is processed by using the generated plasma.

According to a 41st aspect of the present invention, there is provided aplasma processing method according to the 40th aspect, in which beforecontrolling the interior of the vacuum chamber to the specifiedpressure, a straight line passing through a center axis of thehigh-frequency output terminal and a straight line passing through thecenter axis of the high-frequency coupling device are arranged so as tobe generally coincident with each other. The plasma is generated withthe straight line passing through the center axis of the high-frequencyoutput terminal and the straight line passing through the center axis ofthe high-frequency coupling device being generally coincident with eachother.

According to a 42nd aspect of the present invention, there is provided aplasma processing method according to the 40th aspect, in which beforecontrolling the interior of the vacuum chamber at the specifiedpressure, the first variable capacitor and the second variable capacitorare arranged that a straight line passing through a center axis of thesecond variable capacitor and a straight line passing through a centeraxis of the first variable capacitor are generally coincident with eachother. The plasma is generated with the straight line passing throughthe center axis of the second variable capacitor and the straight linepassing through the center axis of the first variable capacitor beinggenerally coincident with each other.

According to a 43rd aspect of the present invention, there is provided aplasma processing method according to the 40th aspect, in which beforecontrolling the interior of the vacuum chamber to the specifiedpressure, the high-frequency output terminal is arranged so as to be theother end itself of the second reactive element. The plasma is generatedwith the high-frequency output terminal being the other end itself ofthe second variable capacitor.

According to a 44th aspect of the present invention, there is provided aplasma processing method according to the 40th aspect, in which beforecontrolling the interior of the vacuum chamber to the specifiedpressure, a substantial distance is arranged from the other end of thesecond variable capacitor to the counter electrode or antenna so as tobe not more than 1/10 of wavelength of the high-frequency power. Theplasma is generated with the substantial distance from the other end ofthe second variable capacitor to the counter electrode or antenna to benot more than 1/10 of wavelength of the high-frequency power.

According to a 45th aspect of the present invention, there is provided aplasma processing apparatus comprising: a vacuum chamber; a gas supplyunit for supplying gas into the vacuum chamber; an evacuating device forevacuating the interior of the vacuum chamber; a substrate electrode forplacing thereon a substrate within the vacuum chamber; a counterelectrode or an antenna provided opposite to the substrate electrode; ahigh-frequency power supply capable of supplying a high-frequency powerhaving a frequency of 50 MHz to 300 MHz to the counter electrode orantenna; the matching box as defined in the 30th aspect; and ahigh-frequency coupling device for connecting the high-frequency outputterminal of the matching box and the counter electrode or antenna toeach other. A straight line passing through a center axis of thehigh-frequency coupling device, a straight line passing through a centeraxis of the counter electrode or antenna, and a straight line passingthrough a center axis of the substrate are arranged so as to begenerally coincident together.

According to a 46th aspect of the present invention, there is provided aplasma processing apparatus according to the 45th aspect, wherein astraight line passing through a center axis of the high-frequency outputterminal and a straight line passing through the center axis of thehigh-frequency coupling device are arranged so as to be generallycoincident with each other.

According to a 47th aspect of the present invention, there is provided aplasma processing apparatus according to the 45th aspect, wherein thefirst reactive element and the second reactive element are arranged sothat a straight line passing through a center axis of the secondreactive element and a straight line passing through a center axis ofthe first reactive element are generally coincident with each other.

According to a 48th aspect of the present invention, there is provided aplasma processing apparatus according to the 45th aspect, wherein thehigh-frequency output terminal is the other end itself of the secondreactive element.

According to a 49th aspect of the present invention, there is provided aplasma processing apparatus according to the 45th aspect, whereinsubstantial distance from the other end of the second reactive elementto the counter electrode or antenna is not more than 1/10 of wavelengthof the high-frequency power.

According to a 50th aspect of the present invention, there is provided aplasma processing apparatus comprising a vacuum chamber; a gas supplyunit for supplying gas into the vacuum chamber; an evacuating device forevacuating the interior of the vacuum chamber; a substrate electrode forplacing thereon a substrate within the vacuum chamber; a counterelectrode or an antenna provided opposite to the substrate electrode; ahigh-frequency power supply capable of supplying a high-frequency powerhaving a frequency of 50 MHz to 300 MHz to the counter electrode orantenna; the matching box as defined in the 30th aspect; and ahigh-frequency coupling device for connecting the high-frequency outputterminal of the matching box and the counter electrode or antenna toeach other. A straight line passing through a center axis of thehigh-frequency coupling device, a straight line passing through a centeraxis of the counter electrode or antenna, and a straight line passingthrough a center axis of the substrate are arranged so as to begenerally coincident together.

According to a 51st aspect of the present invention, there is provided aplasma processing apparatus according to the 50th aspect, wherein theplasma is generated while the straight line passing through the centeraxis of the high-frequency output terminal and the straight line passingthrough the center axis of the high-frequency coupling device arearranged so as to be generally coincident with each other.

According to a 52nd aspect of the present invention, there is provided aplasma processing apparatus according to the 50th aspect, wherein afirst variable capacitor and a second variable capacitor are arranged sothat a straight line passing through a center axis of the secondvariable capacitor and a straight line passing through a center axis ofthe first variable capacitor are generally coincident with each other.

According to a 53rd aspect of the present invention, there is provided aplasma processing apparatus according to the 50th aspect, wherein thehigh-frequency output terminal is the other end itself of the secondvariable capacitor.

According to a 54th aspect of the present invention, there is provided aplasma processing apparatus according to the 50th aspect, wherein asubstantial distance from the other end of the second variable capacitorto the counter electrode or antenna is not more than 1/10 of thewavelength of the high-frequency power.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects and features of the present invention willbecome clear from the following description taken in conjunction withthe preferred embodiments thereof with reference to the accompanyingdrawings, in which:

FIG. 1A is a sectional view showing the constitution of a plasmaprocessing apparatus employed in a first embodiment of the presentinvention;

FIG. 1B is a plan view of plasma trap of the plasma processing apparatusof FIG. 1A;

FIG. 2 is a chart showing measuring results of ion saturation currentdensity in the first embodiment of the present invention;

FIG. 3 is a sectional view showing the constitution of a plasmaprocessing apparatus employed in a second embodiment of the presentinvention;

FIG. 4 is a sectional view showing the constitution of a plasmaprocessing apparatus employed in a third embodiment of the presentinvention;

FIG. 5 is a sectional view showing the constitution of a plasmaprocessing apparatus employed in a fourth embodiment of the presentinvention;

FIG. 6 is a sectional view showing the constitution of a plasmaprocessing apparatus employed in a fifth embodiment of the presentinvention;

FIG. 7 is a sectional view showing the constitution of a plasmaprocessing apparatus employed in a sixth embodiment of the presentinvention;

FIG. 8 is a sectional view showing the constitution of a plasmaprocessing apparatus employed in a seventh embodiment of the presentinvention;

FIG. 9 is a chart showing measuring results of ion saturation currentdensity in the seventh embodiment of the present invention;

FIG. 10 is a sectional view showing the constitution of a plasmaprocessing apparatus employed in an eighth embodiment of the presentinvention;

FIG. 11 is a sectional view showing the constitution of a plasmaprocessing apparatus employed in a ninth embodiment of the presentinvention;

FIG. 12 is a sectional view showing the constitution of a plasmaprocessing apparatus employed in another embodiment of the presentinvention;

FIG. 13 is a sectional view showing the constitution of a plasmaprocessing apparatus employed in another embodiment of the presentinvention;

FIG. 14 is a plan view of the constitution of plasma traps employed inanother embodiment of the present invention;

FIG. 15 is a sectional view showing the constitution of a plasmaprocessing apparatus employed in a prior art example;

FIG. 16 is a sectional view showing the constitution of a plasmaprocessing apparatus employed in a prior art example;

FIG. 17 is a chart showing measuring results of ion saturation currentdensity in a prior art example;

FIG. 18 is a chart showing measuring results of ion saturation currentdensity in a prior art example;

FIG. 19 is a sectional view showing the constitution of a plasmaprocessing apparatus employed in a tenth embodiment of the presentinvention;

FIG. 20 is a chart showing measuring results of ion saturation currentdensity in the tenth embodiment of the present invention;

FIG. 21 is a sectional view showing the constitution of a plasmaprocessing apparatus employed in an eleventh embodiment of the presentinvention;

FIG. 22 is a sectional view showing the constitution of a plasmaprocessing apparatus employed in a twelfth embodiment of the presentinvention;

FIG. 23 is a sectional view showing the constitution of a plasmaprocessing apparatus employed in a thirteenth embodiment of the presentinvention;

FIG. 24 is a sectional view showing the constitution of a plasmaprocessing apparatus employed in a prior art example;

FIG. 25 is a chart showing measuring results of ion saturation currentdensity in the prior art example;

FIG. 26 is a sectional view showing the constitution of a plasmaprocessing apparatus employed in another prior art example;

FIG. 27 is a sectional view showing the constitution of a plasmaprocessing apparatus employed in a modification of the third embodimentof the present invention;

FIG. 28 is a sectional view showing the constitution of a plasmaprocessing apparatus employed in a modification of the eighth embodimentof the present invention;

FIG. 29 is a sectional view showing the constitution of a plasmaprocessing apparatus where the plasma processing apparatus in the tenthembodiment of the present invention in FIG. 19 and the plasma processingapparatus in the modification of the third embodiment of the presentinvention in FIG. 27 are combined with each other; and

FIG. 30 is a sectional view showing the constitution of a plasmaprocessing apparatus where the plasma processing apparatus in theeleventh embodiment of the present invention in FIG. 21 and the plasmaprocessing apparatus in the modification of the eighth embodiment of thepresent invention in FIG. 28 are combined with each other.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Before the description of the present invention proceeds, it is to benoted that like parts are designated by like reference numeralsthroughout the accompanying drawings.

Hereinbelow, embodiments according to the present invention aredescribed in detail with reference to the accompanying drawings.

A first embodiment of the present invention is described below withreference to FIGS. 1A, 1B, and 2.

FIG. 1A shows a sectional view of a plasma processing apparatus employedin the first embodiment of the present invention. Referring to FIG. 1A,while the interior of a vacuum chamber 1 is maintained at a specifiedpressure by introducing a specified gas from a gas supply unit 2 intothe vacuum chamber 1 and by simultaneously performing evacuation by apump 3 as an evacuating device, a high-frequency power of 100 MHz issupplied to a counter electrode 5 by acounter-electrode-use-high-frequency power supply 4. Then, plasma isgenerated in the vacuum chamber 1, where plasma processing such asetching, deposition, and surface reforming can be carried out on asubstrate 7 placed on a substrate electrode 6. Asubstrate-electrode-use-high-frequency power supply 8 for supplyinghigh-frequency power to the substrate electrode 6 is also provided, sothat ion energy that reaches the substrate 7 can be controlled. Also, anannular, groove-like plasma trap 9 shown in FIGS. 1A and 1B is providedopposite to the substrate 7, making it possible to process the substrate7 while the plasma distribution on the substrate 7 is controlled. Theplasma trap 9 is provided in the counter electrode 5. Out of surfacesforming inner wall surfaces of the vacuum chamber 1 and opposing thesubstrate 7, an electrode portion 10 (cross hatched portion) surroundedby the plasma trap 9 has an area 0.8 time that of the substrate 7, asone example. Also, the groove width of the plasma trap 9 is 10 mm, andthe groove depth of the plasma trap 9 is 15 mm, as one example. Inaddition, the counter electrode 5 is insulated from the vacuum chamber 1by an insulating ring 11. As shown in FIG. 1A (as well as the otherFigures), the annular groove (plasma trap) 9 has a bottom face, anouter-side face closest to the side wall of the vacuum chamber 1, and aninner-side face farthest from the side wall of the vacuum chamber 1. Ascan be seen, the outer-side face of the annular groove 9 is located“inside” of the inner surface of the side wall of the vacuum chamber. Inthis regard, the terms “inside” and “outside” mean closer to, andfarther from, respectively, a vertical center axis of the vacuumchamber.

FIG. 2 shows measuring results of ion saturation current density at aposition just 20 mm above the substrate 7. Conditions for plasmageneration are gas type of C12 and gas flow rate of 100 sccm, a pressureof 1 Pa, and a high-frequency power of 2 kW, as one example. It can beunderstood from FIG. 2 that the tendency for plasma to be richer inperipheral regions as shown in FIG. 17 is suppressed, and that uniformplasma is generated.

The reason why the uniformity of plasma is improved like this ascompared with the plasma processing apparatus shown in FIG. 15 of theprior art example could be considered as follows. Electromagnetic wavesradiated from the counter electrode 5 are intensified by the plasma trap9. Also, since plasma of low electron temperature tends to cause hollowcathode discharge, high density plasma (hollow cathode discharge) ismore likely to be generated by the plasma trap 9 surrounded by the solidsurfaces. Accordingly, in the vacuum chamber 1, plasma density becomesthe highest at the plasma trap 9, and through transport of plasma tovicinities of the substrate 7 by diffusion, uniform plasma can beobtained.

In addition, the hollow cathode discharge is as described below.Generally, because a solid surface in contact with plasma is negativelycharged due to differences in thermal motion velocity between electronsand ions, DC electric fields that repel electrons from the solid surfaceare generated on the solid surface. In a space surrounded by solidsurfaces, as in the plasma trap 9 illustrated in the first embodiment ofthe present invention, the probability of electrons colliding with thesolid surfaces is lowered by the presence of the DC electric fields,prolonging the life of the electrons. As a result, high-density plasmais generated in the plasma trap 9. Such a discharge is referred to ashollow cathode discharge.

The first embodiment of the present invention has been described abovefor the case where the plasma trap 9 is provided in the counterelectrode 5. In this case, however, there is a possibility that aself-bias voltage developed at the counter electrode 5 causeshigh-density ions present in the plasma trap 9 to collide with thecounter electrode 5 at a high energy level so that sputtering of thecounter electrode 5 may occur. The sputtering of the counter electrode 5may shorten the life of the counter electrode 5 or mix impurities intothe substrate 7, thus being undesirable. This can be avoided byproviding the plasma trap in portions other than the counter electrode5. For example, the plasma trap 9 may be provided in the insulating ring11 as shown in a second embodiment of FIG. 3. Also, the plasma trap 9may be provided outside the insulating ring 11, that is, in a metallicupper wall 1 a of the vacuum chamber 1 as shown in a third embodiment ofFIG. 4. Further, when the plasma trap 9 is provided between the counterelectrode 5 and the insulating ring 11 as shown in a fourth embodimentof FIG. 5 or a fifth embodiment of FIG. 6, improvement can be attainedmore or less. Furthermore, the plasma trap 9 may be provided between theupper wall 1 a of the vacuum chamber 1 and the insulating ring 11 asshown in a sixth embodiment of FIG. 7.

In FIG. 1A, the plasma trap 9 is defined by three faces, that is, aninner face, an upper face, and an outer face of the counter electrode 5.In FIG. 3, the plasma trap 9 is defined by three faces, that is, aninner face, an upper face, and an outer face of the insulating ring 11.In FIG. 4, the plasma trap 9 is defined by three faces, that is, aninner face, an upper face, and an outer face of the upper wall 1 a ofthe vacuum chamber 1. In FIG. 5, the plasma trap 9 is defined by aninner face formed on the counter electrode 5 and an upper face and anouter face formed on the insulating ring 11. In FIG. 6, the plasma trap9 is defined by an inner face and an upper face formed on the counterelectrode 5 and an outer face formed on the insulating ring 11 and theupper wall 1 a of the vacuum chamber 1. In FIG. 7, the plasma trap 9 isdefined by an inner face formed on the insulating ring 11 and an upperface and an outer face formed on the upper wall 1 a of the vacuumchamber 1.

Next, a seventh embodiment of the present invention is described withreference to FIGS. 8 and 9.

FIG. 8 shows a sectional view of a plasma processing apparatus employedin the seventh embodiment of the present invention. Referring to FIG. 8,while the interior of a vacuum chamber 1 is maintained at a specifiedpressure by introducing a specified gas from a gas supply unit 2 intothe vacuum chamber 1 and simultaneously performing evacuation by a pump3 as an evacuating device, a high-frequency power of 100 MHz is suppliedto a spiral antenna 13 by an antenna-use-high-frequency power supply 12,and electromagnetic waves are radiated into the vacuum chamber 1 via adielectric window 14 provided opposite the substrate 7 placed on thesubstrate electrode 6. Then, plasma is generated in the vacuum chamber1, where plasma processing such as etching, deposition, and surfacereforming can be carried out on the substrate 7. Asubstrate-electrode-use-high-frequency power supply 8 for supplyinghigh-frequency power to the substrate electrode 6 is provided, so thation energy that reaches the substrate 7 can be controlled. Also, anannular, groove-like plasma trap 9 provided opposite to the substrate 7makes it possible to process the substrate 7 while the plasmadistribution on the substrate 7 is controlled. The plasma trap 9 isprovided in the dielectric window 14 so as to be defined by an inner, anupper, and an outer faces formed in the dielectric window 14. Out ofsurfaces of the vacuum chamber 1 opposing the substrate 7, a wallportion 10 (cross hatched portion) surrounded by the plasma trap 9 hasan area 0.8 time that of the substrate 7, as one example. Also, thegroove width of the plasma trap 9 is 10 mm, and the groove depth of theplasma trap 9 is 15 mm, as one example.

FIG. 9 shows measuring results of ion saturation current density at aposition just 20 mm above the substrate 7. Conditions for plasmageneration are gas type of Cl₂ and gas flow rate of 100 sccm, a pressureof 1 Pa, and a high-frequency power of 2 kW, as one example. It can beunderstood from FIG. 9 that the tendency for plasma to be richer inperipheral regions as shown in FIG. 18 is suppressed, and that uniformplasma is generated.

The reason why the uniformity of plasma is improved like this ascompared with the plasma processing apparatus shown in FIG. 16 of theprior art example could be considered as follows. Electromagnetic wavesradiated from the spiral antenna 13 are intensified by the plasma trap9. Also, since plasma of low electron temperature tends to cause hollowcathode discharge, high density plasma (hollow cathode discharge) ismore likely to be generated by the plasma trap 9 surrounded by the solidsurfaces. Accordingly, in the vacuum chamber 1, plasma density becomesthe highest at the plasma trap 9, and through transport of plasma tovicinities of the substrate 7 by diffusion, uniform plasma can beobtained.

The 7th embodiment of the present invention has been described above forthe case where the plasma trap 9 is provided in the dielectric window14. However, the plasma trap 9 may also be provided outside thedielectric window 14 so as to be defined by three faces, that is, aninner face, an upper face, and an outer face formed in the upper wall 1a of the vacuum chamber 1 as shown in an eighth embodiment of FIG. 10.Further, the plasma trap 9 may be provided between the vacuum chamber 1and the dielectric window 14 so as to be defined by three faces, thatis, an inner face and an upper face formed by the dielectric window 14,and an outer face formed by the upper wall 1 a of the vacuum chamber 1as shown in a 9th embodiment of FIG. 11. As shown in FIGS. 10 and 11,the plasma trap 9 can be arranged in the upper surface of the vacuumchamber so that the outer diameter of the plasma trap is less than theinner side surface diameter of the vacuum chamber, and a that a metallicsurface portion 1 a is formed between the outer periphery of the plasmatrap and the inner side surface of the vacuum chamber 1.

The foregoing embodiments of the present invention as described aboveare given only by way of example as part of many variations of theconfiguration of the vacuum chamber 1, the configuration and arrangementof the counter electrode 6 or antenna 13, the configuration andarrangement of the dielectric window 14, and the configuration andarrangement of the plasma trap 9, within the application scope of thepresent invention. It is needless to say that the present invention maybe applied in other various ways besides the examples given above. Forexample, whereas the foregoing embodiments have been described for thecase where the counter electrode 6 is circular shaped, the counterelectrode may also be formed in a polygonal, elliptical, or other shape.Also, whereas in each of the foregoing cases, the antenna 13 is spiralshaped, the antenna may be formed in a flat-plate, spoke, or othershape. Otherwise, the present invention may also be applied to asurface-wave plasma processing apparatus having a cavity resonator 15,as shown in FIG. 12, where the cavity resonator 15 is regarded as anantenna. Furthermore, the present invention may be applied to asurface-wave plasma processing apparatus having a cavity resonator 15and a slot antenna 16, as shown in FIG. 13.

The foregoing embodiments of the present invention have been describedfor the case where the plasma trap 9 is annular shaped. However, theplasma trap 9 may also be formed into a polygonal, elliptical, or othershape in accordance with the configuration of the substrate 7.Otherwise, the plasma trap 9 may be formed into a shape that is not aclosed annular shape but a divisional, yet generally annular shape asshown by the plan view of FIG. 14. The above various kinds ofarrangement of the plasma trap 9 in FIGS. 8, 10, and 11 etc. can beapplied to the apparatus of FIGS. 12 and 13.

Further, whereas the first or seventh embodiment of the presentinvention has been described for the case where a high-frequency powerof 100 MHz is supplied to the counter electrode 6 or antenna 13, thefrequency is not limited to this and the present invention is effectivefor a plasma processing method and apparatus using frequencies of 50 MHzto 3 Ghz.

Also, each of the first to seventh embodiments of the present inventionhas been described for the case where, out of surfaces forming the innerwall surfaces of the vacuum chamber 1 and opposing the substrate 7, thearea of the portion surrounded by the plasma trap 9 is 0.8 times thearea of the substrate 7. However, it is desirable that the area of thisportion be 0.5-2.5 times the area of the substrate 7. If the area ofthis portion is less than 0.5 times the area of the substrate 7, it isdifficult to obtain uniform plasma in vicinities of the substrate 7 evenwith a sufficient distance between the substrate 7 and the plasma trap9. Also, if the area of this portion is over 2.5 times the area of thesubstrate 7, it is necessary to keep an extremely large distance betweenthe substrate 7 and the plasma trap 9 in order to obtain uniform plasmain vicinities of the substrate 7. This, undesirably, would cause theapparatus to be increased in size, and an excessive burden would beimposed on the pump 3 to hold the interior of the vacuum chamber 1 at alow pressure. For example, when the substrate has a diameter of 300 mmand the plasma trap has a diameter of 200 mm, the area of this portionsurrounded by the plasma trap is 0.5 times the area of the substrate.When the substrate has a diameter of 300 mm and the plasma trap has adiameter of 300 mm, the area of this portion surrounded by the plasmatrap is 2.5 times the area of the substrate.

Also, each of the first to seventh embodiments of the present inventionhas been described for the case where the groove width of the plasmatrap 9 is 10 mm. However, it is desirable that the groove width of theplasma trap 9 be within a range of 3 mm-50 mm. If the groove width isless than 3 mm, or over 50 mm, there is a possibility that hollowcathode discharge does not occur by the plasma trap 9.

Also, whereas the foregoing embodiments have been described for the casewhere the groove of the plasma trap 9 is rectangular section-shaped, thegroove sectional shape may be U-shaped, V-shaped, or a combination ofrectangular shape, U-shape, and V-shape.

Also, each of the first to seventh embodiments of the present inventionhas been described for the case where the groove depth of the plasmatrap 9 is 15 mm. However, it is desirable that the groove depth of theplasma trap 9 be not less than 5 mm. If the groove depth is less than 5mm, there is a possibility that hollow cathode discharge does not occur.

The plasma processing apparatus of the third embodiment in FIGS. 4 and10 may be applied in a case where the area surrounded by the plasma trap9 is larger than the area of the substrate 7. In this case, it issuitable to use per-fluorocarbon gas such as CF₄ gas, C₂F₆ gas, C₄F₈gas, C₅F₈ gas, etc. or hydro-fluorocarbon such as CHF₃ gas, CH₂F₂, etc.

On the other hand, a plasma processing apparatus of a modification ofthe third embodiment in FIG. 27 and a plasma processing apparatus of amodification of the eighth embodiment in FIG. 28 may be applied in acase where the area surrounded by the plasma trap 9 is not larger thanthe area of the substrate 7. In this case, it is suitable to useBoron-based gas such as HBr gas, or chlorine-based gas such as Cl₂ gas,BCl₃ gas, HCl gas etc.

Please note that although it has been described as one example that theusing gas is applied depending on the area surrounded by the plasmatrap, the optimum selection of the using gas is not limited to this. Theoptimum condition can be determined while referring to pressure, power,mixed gas, and the like because the optimum selection of the using gasdepends on the conditions such as pressure, power, mixed gas, and thelike.

Also, the foregoing embodiments of the present invention have beendescribed for the case where DC magnetic fields are absent in the vacuumchamber 1. However, the present invention is also effective for caseswhere such large DC magnetic fields as to allow high-frequency power topenetrate into the plasma are absent, for example, a case where small DCmagnetic fields on the order of several tens gausses are used forimprovement in ignitability. Yet, the present invention is particularlyeffective for cases where DC magnetic fields are absent in the vacuumchamber 1.

As apparent from the above description, the plasma processing method ofthe present invention for generating plasma within a vacuum chamber andprocessing a substrate placed on a substrate electrode within the vacuumchamber comprises generating the plasma by supplying a high-frequencypower having a frequency of 50 MHz to 3 GHz to a counter electrodeprovided opposite to the substrate while the interior of the vacuumchamber is controlled to maintain a specified pressure by introducinggas into the vacuum chamber. Simultaneously, therewith, the interior ofthe vacuum chamber is evacuated. The substrate is processed by using thegenerated plasma while distribution of the plasma on the substrate iscontrolled by an annular, groove-like plasma trap provided opposite tothe substrate. Thus, because the substrate is processed while the plasmadistribution on the substrate is controlled by the annular, groove-likeplasma trap provided opposite to the substrate, uniform plasma can begenerated so that the substrate can be uniformly processed.

Also, the plasma processing method of the present invention forgenerating plasma within a vacuum chamber and processing a substrateplaced on a substrate electrode within the vacuum chamber comprisesgenerating the plasma by radiating electromagnetic waves into the vacuumchamber via a dielectric window provided opposite to the substrate bysupplying a high-frequency power having a frequency of 50 MHz to 3 GHzto an antenna while the interior of the vacuum chamber is controlled tomaintain a specified pressure by introducing gas into the vacuumchamber. Simultaneously, therewith, the interior of the vacuum chamberis evacuated. The substrate is processed by using the generated plasmawhile plasma distribution of the plasma on the substrate is controlledby an annular, groove-like plasma trap provided opposite to thesubstrate. In this method, if the substrate is processed while theplasma distribution on the substrate is controlled by the annular,groove-like plasma trap provided opposite to the substrate, uniformplasma can be generated so that the substrate can be uniformlyprocessed.

Also, the plasma processing apparatus of the present invention comprisesa vacuum chamber; a gas supply unit for supplying gas into the vacuumchamber; an evacuating device for evacuating the interior of the vacuumchamber; a substrate electrode for placing thereon a substrate withinthe vacuum chamber; a counter electrode provided opposite to thesubstrate electrode; high-frequency power supply capable of supplying ahigh-frequency power having a frequency of 50 MHz to 3 GHz to thecounter electrode; and an annular, groove-like plasma trap providedopposite to the substrate. Thus, uniform plasma can be generated so thatthe substrate can be uniformly processed.

Also, the plasma processing apparatus of the present invention comprisesa vacuum chamber; a gas supply unit for supplying gas into the vacuumchamber; an evacuating device for evacuating the interior of the vacuumchamber; a substrate electrode for placing thereon a substrate withinthe vacuum chamber; a dielectric window provided opposite to thesubstrate electrode; an antenna for radiating electromagnetic waves intothe vacuum chamber via the dielectric window; a high-frequency powersupply capable of supplying a high-frequency power having a frequency of50 MHz to 3 GHz to the antenna; and an annular, groove-like plasma trapprovided opposite to the substrate. Thus, uniform plasma can begenerated so that the substrate can be uniformly processed.

Now a tenth embodiment of the present invention is described below withreference to FIGS. 19 and 20.

FIG. 19 shows a sectional view of a plasma processing apparatus employedin the tenth embodiment of the present invention. Referring to FIG. 19,while the interior of a vacuum chamber 101 is maintained at a specifiedpressure by introducing a specified gas from a gas supply unit 102 intothe vacuum chamber 101 and simultaneously performing evacuation by apump 103 as an evacuating device, a high-frequency power of 100 MHz issupplied to a counter electrode 107 by acounter-electrode-use-high-frequency power supply 104 via a matching box105 and a high-frequency coupling device (mount) 106. Then, plasma isgenerated in the vacuum chamber 101, where plasma processing such asetching, deposition, and surface reforming can be carried out on asubstrate 109 placed on a substrate electrode 108. Asubstrate-electrode-use-high-frequency power supply 110 for supplyinghigh-frequency power to the substrate electrode 108 is also provided, sothat ion energy that reaches the substrate 109 can be controlled. Inaddition, the counter electrode 107 is insulated from the vacuum chamber101 by an insulating ring 111.

The matching box 105, which is used to take impedance matching insupplying high-frequency power to the counter electrode 107 as a load,comprises a high-frequency input terminal 112, a first variablecapacitor 113, a high-frequency output terminal 114, a second variablecapacitor 115, a first motor 116, a second motor 117, and a motorcontrol circuit 118. One end of the first variable capacitor 113 isconnected to the high-frequency input terminal 112, the other end beingconnected to the matching box casing 105 a. One end of the secondvariable capacitor 115 is connected to the high-frequency input terminal112, the other end being connected to the high-frequency output terminal114. Also, a straight line forming the center axis of the secondvariable capacitor 115, a straight line forming the center axis of thehigh-frequency output terminal 114, a straight line forming the centeraxis of the high-frequency coupling device (mount) 106, a straight lineforming the center axis of the counter electrode 107, and a straightline forming the center axis of the substrate 109 are arranged so as tobe generally coincident together. Also, the first variable capacitor 113and the second variable capacitor 115 are arranged so that the straightline forming the center axis of the second variable capacitor 115 and astraight line forming the center axis of the first variable capacitor113 are generally coincident with each other. Further, a substantialdistance 19 from the other end of the second variable capacitor 115 tothe counter electrode 107 is 1/15 (20 cm) of the wavelength (3 m) of thehigh-frequency power, as one example.

FIG. 20 shows results of measuring ion saturation current density atapposition just 20 mm above the substrate 109. Conditions for plasmageneration are gas type of Cl₂ and gas flow rate of 100 sccm, a pressureof 2 Pa, and a high-frequency power of 1 kW, as one example. Also, FIG.19 shows the measuring position in FIG. 20. It can be understood fromFIG. 20 that nonuniformity of plasma as shown in FIG. 25, where plasmadensity is higher on one side of the measuring position, cannot be seen.

The reason why the uniformity of plasma is improved like this ascompared with the plasma processing apparatus shown in FIG. 24 of theprior art example could be considered as follows. In the case where ahigh-frequency power of 50 MHz or higher is used, there develops apotential distribution in the counter electrode 107 under the effect ofthe arrangement of the second variable capacitor 115 within the matchingbox 105. However, in the tenth embodiment of the present invention, thepotential distribution developed on the counter electrode 107 becomesconcentric because of the arrangement in which a straight line formingthe center axis of the second variable capacitor 115, a straight lineforming the center axis of the high-frequency output terminal 114, astraight line forming the center axis of the high-frequency couplingdevice (mount) 106, a straight line forming the center axis of thecounter electrode 107, and a straight line forming the center axis ofthe substrate 109 are generally coincident together. As a result, theelectric fields within the vacuum chamber 101 also become concentric sothat the uniformity of plasma can be improved.

The foregoing tenth embodiment of the present invention has beendescribed for the case where the counter electrode 107 is used togenerate plasma. However, the present invention is also effective forcases where a spiral antenna 120 is used as in an eleventh embodiment ofthe present invention shown in FIG. 21. In addition, in the eleventhembodiment of the present invention shown in FIG. 21, a dielectricwindow 121 is used.

Also, the foregoing tenth and eleventh embodiments of the presentinvention are given only by way of example as part of many variations ofthe configuration of the vacuum chamber 101, the configuration andarrangement of the counter electrode 107 or antenna 120, theconfiguration and arrangement of the dielectric 121, and the like withinthe application scope of the present invention. It is needless to saythat the present invention may be applied in other various ways besidesthe examples given above. For example, whereas the tenth embodiment ofthe present invention has been described for a case where the counterelectrode 107 is circular shaped, the counter electrode may also beformed in a polygonal, elliptical, or other shape. Also, whereas in theforegoing case, the antenna 120 is spiral shaped, the antenna may beformed in a flat-plate, spoke, or other shape.

The foregoing 10th and 11th embodiments of the present invention havebeen described for the case where the high-frequency power of 100 MHz issupplied to the counter electrode 107 or antenna 120. However, thefrequency is not limited to this and the present invention is effectivefor cases where frequencies of 50 MHz to 300 MHz are used. If thefrequency is lower than 50 MHz, the uniformity of plasma can be easilyobtained even without applying the present invention. Also, if thefrequency is higher than 300 MHz, it is difficult to take impedancematching by using two variable capacitors, giving rise to a need fortaking impedance matching by stubs.

Also, the 10th and 11th embodiments of the present invention have beendescribed for a case where the first variable capacitor and the secondvariable capacitor are arranged so that the straight line forming thecenter axis of the second variable capacitor and the straight lineforming the center axis of the first variable capacitor are generallycoincident with each other. However, because the potential distributiondeveloped at the counter electrode 107 is affected primarily by thearrangement of the second variable capacitor, the uniformity of plasmais greatly improved, as compared with the prior art, also when thestraight line forming the center axis of the second variable capacitor115 and the straight line forming the center axis of the first variablecapacitor 113 are not coincident with each other as in a 12th embodimentof the present invention shown in FIG. 22. Such a constitution as shownin FIG. 22 is effective for cases where the matching box needs to bedownsized, the constitution being included in the application scope ofthe present invention.

Also, the 12th embodiment of the present invention has been describedfor the case where the matching box has variable capacitors by way ofexample. However, the present invention produces similar effects alsowith a matching box having reactive elements such as variable inductors,fixed capacitors, or fixed inductors.

Also, whereas the 12th embodiment has been described for the case wherethe other end of the second variable capacitor 115 and thehigh-frequency output terminal are provided as separate members.However, the high-frequency output terminal 114 may be provided as theother end of the second variable capacitor 115 itself, as in a 13thembodiment of the present invention shown in FIG. 23.

Also, the 10th embodiment of the present invention has been described onthe case where the substantial distance from the other end of the secondvariable capacitor 115 to the counter electrode 107 is 1/15 of thewavelength of the high-frequency power. It is desirable that thesubstantial distance from the other end of the second variable capacitor115 to the counter electrode 107 or antenna 120 be 1/10 or less of thewavelength of the high-frequency power. If the substantial distance fromthe other end of the second variable capacitor 115 to the counterelectrode 107 or antenna is larger than 1/10 of the wavelength of thehigh-frequency power, the inductance from the other end of the secondvariable capacitor 115 to the counter electrode 107 or antenna becomestoo large, making it difficult to take impedance matching with twovariable capacitors.

In the foregoing embodiments, any one of the embodiments can be combinedwith any other one of the embodiments. For example, FIG. 29 is asectional view showing the constitution of a plasma processing apparatuswhere the plasma processing apparatus in the tenth embodiment of thepresent invention in FIG. 19 and the plasma processing apparatus in themodification of the third embodiment of the present invention in FIG. 27are combined with each other. FIG. 30 is a sectional view showing theconstitution of a plasma processing apparatus where the plasmaprocessing apparatus in the eleventh embodiment of the present inventionin FIG. 21 and the plasma processing apparatus in the modification ofthe eighth embodiment of the present invention in FIG. 28 are combinedwith each other. Such a combination can obtain both of the effects ofthe combined embodiments.

As apparent from the above description, the matching box of the presentinvention is for use in a plasma processing apparatus and for takingimpedance matching in supplying high-frequency power to a load. Thematching box comprises a high-frequency input terminal; a first reactiveelement having one end connected to the high-frequency input terminaland the other end connected to a matching box casing; a high-frequencyoutput terminal; and a second reactive element having one end connectedto the high-frequency input terminal and the other end connected to thehigh-frequency output terminal. The second reactive element and thehigh-frequency output terminal are arranged so that the second reactiveelement is located on a straight line passing through a center axis ofthe high-frequency output terminal. Thus, uniform plasma can begenerated so that the substrate can be uniformly processed.

Also, the matching box of the present invention is for use in a plasmaprocessing apparatus and for taking impedance matching in supplyinghigh-frequency power to a load. The matching box comprises ahigh-frequency input terminal; a first variable capacitor having one endconnected to the high-frequency input terminal and the other endconnected to a matching box casing; a high-frequency output terminal;and a second variable capacitor having one end connected to thehigh-frequency input terminal and the other end connected to thehigh-frequency output terminal. The second variable capacitor and thehigh-frequency output terminal are arranged so that the second variablecapacitor is located on a straight line passing through a center axis ofthe high-frequency output terminal. Thus, uniform plasma can begenerated so that the substrate can be uniformly processed.

Also, the plasma processing method of the present invention includesgenerating plasma within a vacuum chamber and processing a substrateplaced on a substrate electrode within the vacuum chamber. The methodcomprises arranging a straight line passing through a center axis of thehigh-frequency coupling device, a straight line passing through a centeraxis of the counter electrode or antenna, and a straight line passingthrough a center axis of the substrate so as to be generally coincidenttogether. The interior of the vacuum chamber is maintained at aspecified pressure by introducing a gas into the vacuum chamber and,simultaneously therewith, exhausting the interior of the vacuum chamber.The plasma is generated by applying a high-frequency power having afrequency of 50 MHz to 300 MHz to a counter electrode or antennaprovided opposite to the substrate via the matching box, and ahigh-frequency coupling device is provided to connect a high-frequencyoutput terminal of the matching box and the counter electrode or antennato each other. The substrate is processed by using the generated plasma.Thus, uniform plasma can be generated so that the substrate can beuniformly processed.

Also, the plasma processing method of the present invention is forgenerating plasma within a vacuum chamber and processing a substrateplaced on a substrate electrode within the vacuum chamber. The methodcomprises arranging a straight line passing through a center axis of thehigh-frequency coupling device, a straight line passing through a centeraxis of the counter electrode or antenna, and a straight line passingthrough a center axis of the substrate so as to be generally coincidenttogether. The interior of the vacuum chamber is maintained at aspecified pressure by introducing a gas into the vacuum chamber and,simultaneously therewith, exhausting the interior of the vacuum chamber.The plasma is generated by applying a high-frequency power having afrequency of 50 MHz to 300 MHz to a counter electrode or antennaprovided opposite to the substrate via the matching box, and ahigh-frequency coupling device is provided to connect a high-frequencyoutput terminal of the matching box and the counter electrode or antennato each other. The substrate is processed by using the generated plasma.Thus, uniform plasma can be generated so that the substrate can beuniformly processed.

Also, the plasma processing apparatus comprises a vacuum chamber; a gassupply unit for supplying gas into the vacuum chamber; an evacuatingdevice for evacuating the interior of the vacuum chamber; a substrateelectrode for placing thereon a substrate within the vacuum chamber; acounter electrode or an antenna provided opposite to the substrateelectrode; a high-frequency power supply capable of supplying ahigh-frequency power having a frequency of 50 MHz to 300 MHz to thecounter electrode or antenna; the matching box as defined in the 28thaspect; and a high-frequency coupling device for connecting thehigh-frequency output terminal of the matching box and the counterelectrode or antenna to each other. A straight line passing through acenter axis of the high-frequency coupling device, a straight linepassing through a center axis of the counter electrode or antenna, and astraight line passing through a center axis of the substrate arearranged so as to be generally coincident together. Thus, uniform plasmacan be generated so that the substrate can be uniformly processed.

Also, the plasma processing apparatus comprises a vacuum chamber; a gassupply unit for supplying gas into the vacuum chamber; an evacuatingdevice for evacuating the interior of the vacuum chamber; a substrateelectrode for placing thereon a substrate within the vacuum chamber; acounter electrode or an antenna provided opposite to the substrateelectrode; high-frequency power supply capable of supplying ahigh-frequency power having a frequency of 50 MHz to 300 MHz to thecounter electrode or antenna; the matching box as defined in the 33rdaspect; and a high-frequency coupling device for connecting thehigh-frequency output terminal of the matching box and the counterelectrode or antenna to each other. A straight line passing through acenter axis of the high-frequency coupling device, a straight linepassing through a center axis of the counter electrode or antenna, and astraight line passing through a center axis of the substrate arearranged so as to be generally coincident together. Thus, uniform plasmacan be generated so that the substrate can be uniformly processed.

Although the present invention has been fully described in connectionwith the preferred embodiments thereof with reference to theaccompanying drawings, it is to be noted that various changes andmodifications are apparent to those skilled in the art. Such changes andmodifications are to be understood as included within the scope of thepresent invention as defined by the appended claims unless they departtherefrom.

1. A plasma processing method for generating plasma within a vacuumchamber and processing a substrate placed on a substrate electrodewithin the vacuum chamber, the method comprising: generating the plasmaby supplying a high-frequency power having a frequency of 50 MHz to 3GHz to a counter electrode provided opposite to the substrate while theinterior of the vacuum chamber is controlled to a specified pressure byintroducing gas into the vacuum chamber and, simultaneously therewith,evacuating the interior of the vacuum chamber; and processing thesubstrate using the generated plasma while controlling plasmadistribution on the substrate using a single annular groove formedbetween the vacuum chamber and an insulating ring for insulating thevacuum chamber and the counter electrode from each other, wherein saidinsulating ring annularly surrounds the counter electrode, wherein theannular groove being located so that an outer-side face of the annulargroove is located inside of and is non-coplanar with an inner surface ofa sidewall of the vacuum chamber, and so that the annular groove has agroove width in a range of 3 mm to 50 mm.
 2. A plasma processingapparatus comprising: a vacuum chamber; a gas supply unit for supplyinggas into said vacuum chamber; an evacuating device for evacuating aninterior of said vacuum chamber; a substrate electrode for placingthereon a substrate within said vacuum chamber; a counter electrodeprovided opposite to said substrate electrode; a high-frequency powersupply operable to supply a high-frequency power having a frequency of50 MHz to 3 GHz to said counter electrode; and a single annular grooveformed between said vacuum chamber and an insulating ring for insulatingsaid vacuum chamber and said counter electrode from each other, whereinsaid insulating ring annularly surrounds the counter electrode, whereinsaid annular groove being located so that an outer-side face of saidannular groove is located inside of and is non-coplanar with an innersurface of a sidewall of said vacuum chamber, said annular groove havinga groove width in a range of 3 mm to 50 mm.
 3. The plasma processingmethod of claim 1, wherein the single annular groove defines a plasmatrap located opposite the substrate.
 4. The plasma processing method ofclaim 1, further comprising supplying a gas into the vacuum chamber at alocation outside of the annular groove such that no gas is introduceddirectly into the annular groove from outside the vacuum chamber.
 5. Theplasma processing apparatus of claim 2, wherein said single annulargroove defines a plasma trap located opposite the substrate.
 6. Theplasma processing apparatus of claim 2, further comprising a gas inletfor introducing a gas into the vacuum chamber, said gas inlet beinglocated such that no gas is introduced directly into the annular groovefrom outside the vacuum chamber.
 7. The plasma processing apparatus ofclaim 2, wherein said vacuum chamber includes an upper wall, saidannular groove being located between said upper wall of said vacuumchamber and said insulating ring.
 8. The plasma processing method ofclaim 1, wherein an entirety of the annular groove is spaced apart fromthe inner surface of the sidewall of the vacuum chamber.
 9. The plasmaprocessing method of claim 1, wherein the annular groove is locatedbetween a surface of an upper wall of the vacuum chamber and theinsulating ring.
 10. The plasma processing method of claim 9, whereinthe annular groove is located so that a shoulder portion of the upperwall is located between the outer-side face of the annular groove andthe inner surface of the sidewall of the vacuum.
 11. The plasmaprocessing method of claim 1, wherein the outer-side face of the annulargroove is a surface different from the inner surface of the sidewall ofthe vacuum chamber.
 12. The plasma processing apparatus of claim 2,wherein an entirety of said annular groove is spaced apart from saidinner surface of said sidewall of said vacuum chamber.
 13. The plasmaprocessing apparatus of claim 2, wherein said annular groove is locatedbetween a surface of an upper wall of said vacuum chamber and saidinsulating ring.
 14. The plasma processing apparatus of claim 13,wherein said annular groove is located so that a shoulder portion ofsaid upper wall is located between said outer-side face of said annulargroove and said inner surface of said sidewall of said vacuum.
 15. Theplasma processing apparatus of claim 2, wherein said outer-side face ofsaid annular groove is a surface different from said inner surface ofsaid sidewall of said vacuum chamber.